Two component polyurethane coatings are used in a variety of applications. For some of these applications, the coating is applied to the substrate via a spray gun. Spray applications typically require the use of solvent additives to reduce the viscosity of the coating composition into a range compatible with the spray gun. Unfortunately, high levels of solvent additives may lead to increased volatile organic compound (VOC) levels in the resultant polyurethane coatings, which in turn, may lead to increased concerns regarding the toxicity of the coatings. In particular, VOCs are organic chemicals that have a high vapor pressure at ordinary room temperature (or low boiling point), which may cause large numbers of molecules to evaporate or sublimate from the coating and enter the surrounding air. VOCs are typically regulated by law.
Accordingly, there is a need for polyurethane coating compositions that reduce the use of such solvent additives that provide increased VOC levels in the resultant coatings, while still providing desirable coating properties (such as hardness and UV weatherability).